Fluidic device

ABSTRACT

A fluidic device comprising an inlet passage for receiving a heat vaporizable supply liquid, a main power nozzle connected to the inlet passage, a pair of outlet passages communicated through an interaction chamber with the outlet of the power nozzle and at least one, preferably a pair of by-pass control passages for directing the main stream of liquid through the device to one or the other of the outlet passages. The by-pass control passage communicates the inlet passage directly with the interaction chamber by-passing the power nozzle. It includes heating means for vaporizing the flow of liquid therethrough. A small portion of the main liquid stream through the inlet passage of the device is diverted to the control bypass to be used as control flow. During passage through the control by-pass, the control liquid flow may be vaporized into gas flow by heating means. The vaporization of the control liquid causes a decrease in the mass flow of the control fluid which is effective to produce a transverse pressure differential across the main liquid stream through the interaction chamber sufficient to bias it for flow through the desired one of the two outlet passages. A refrigeration system includes a pair of evaporators, means for supplying a liquid refrigerant to the evaporators and a fluidic device of the type described. The fluidic device is provided between refrigerant supplying means and a pair of evaporators with its inlet passage connected to refrigerant supplying means for receiving the refrigerant and each of its two outlet passages connected to respective one of the evaporators. Heating means on the control by-passes are adapted to be operated in response to predetermined temperature conditions within the spaces where the evaporators are disposed so as to bias the flow of refrigerant through the fluidic device to one or the other of its outlet passages for supply into corresponding one of the evaporators.

United States Patent 91 Suzuki et a1.

[54] FLUIDIC DEVICE [75] Inventors: Fumio Suzuki; Furnio Naito; ShojiSugaya, all of Osaka, Japan [73] Assignee: Sanyo Electric Co., Ltd.,Osaka,

Japan [22] Filed: Aug. 20, 1970 [21] Appl. No.: 65,492

[30] Foreign Application Priority Data Aug. 23, 1969 Japan ..44/66596[52] 11.8. C1 ..'.T ..';....'....;.137/807 [51] Int. Cl. ..Fl5c l/04[58] Field of Search l37/81.5

[56] References Cited UNITED STATES PATENTS 3,452,767 7/1969 Posingies 137/8 1 .5

3,275,014 9/1966 Plasko ..l37/8l.5 3,290,893 12/1966 l-laldopoulos.... 137/815 X 3,348,562 10/1967 Ogren ..l37/8l.5

3,361,149 1/1968 Meyer ..137/8l.5

3,388,862 6/1968 Gabrielson 137/815 X 3,420,255 l/1969 Wilkerson..137/8l.5

3,509,896 5/1970 Bowles 1 37/8 1 .5 3,513,706 Berrey ..l37/8l.5 X

Primary Examiner-Samuel Scott Attorney-Darby & Darby [5 7 ABSTRACT powernozzle connected to the inlet passage, a pair of outlet passagescommunicated through an interaction chamber with the outlet of the powernozzle and at least one, preferably a pair of by-pass control passages.for directing the main stream of, liquid through the device to one orthe other of the outlet passages. The by-pass control passagecommunicates the inlet passage directly with the interaction chamberbypassing the power nozzle.

It includes heating means for vaporizing the flow of liquidtherethrough. A small portion of the main liquid stream through theinlet passage of the device is diverted to the control by-pass to beused as control flow. During passage through the control by-pass, thecontrol liquid flow may be vaporized into gas flow by heating means. Thevaporization of the control liquid causes a decrease in the mass flow ofthe control fluid which is effective to produce a transverse pressuredifferential across the main liquid stream through the interactionchamber sufficient to bias it for flow through the desired one of thetwo outlet passages.

A refrigeration system includes a pair of evaporators, means forsupplying a liquid refrigerant to the evaporators and a fluidic deviceof the type described. The fluidic device is provided betweenrefrigerant supplying means and a pair of evaporators with its inletpassage connected to refrigerant supplying means for receiving therefrigerant and each of its two outlet passages connected to respectiveone of the evaporators. Heating means on the control by-passes' areadapted to be operated in response to predetermined temperatureconditions within the spaces where the evaporators are disposed so as tobias the flow of refrigerant through the fluidic device to one or theother of its outlet passages for supply into corresponding one of theevaporators.

12 Claims, 8 Drawing Figures 2a 2&0 27a 22a 22 PATENTEUuAmmm SHEET 1 BF3 E 2mm 2? 2/4 22? 3 FLUIDIC DEVICE BACKGROUND OF THE INVENTION Thisinvention relates to a thermally controlled fluidic device and anapparatus having such fluid device incorporated therein.

Fluidic devices have been known and used primarily in logic circuitapplications. Such devices also offer distinct advantages as reliablelow cost value means for controlling relatively large volume flows ofliquid in recirculation systems. The desired control function isaccomplished by the actions and interactions of moving fluid without theaid of mechanical moving parts such as flappers, piston, or diaphragmsThe absence of the mechanical moving parts in a fluidic device assuresdependable, trouble-free control operation for a extended period oftime. Although such is the nature of the fluidic device itself,conventional fluidic devices generally have associated auxiliarymechanism for providing requisite control input in the form of controlflow of fluid to the control port or ports of the devices and one ormore mechanical moving parts are inevitably included in the mechanism.For example, some conventional fluidic devices have one or two controlports and they are connected to a control fluid source for receiving thecontrol flow of fluid which is the control input to the device. Thecontrol fluid source is separate from and independent of a main powersource of the fluidic device and the supply of the control flow of fluidto the control ports are controlled by suitable valve means such assolenoid valves, throttle valves, flappers, or diaphragms which areinterposed between the control source and the control ports of thefluidic device. The fact that mechanical valve means are con-.

nected to the control ports of the fluidic device and that they areeasily subject to operational troubles and difficulties due to, forexample, abrasion, wear down and the like tend to kill or offset thedistinct advantages of the fluidic device itself. Accordingly, in orderto make the best use of the benefits inherent to the fluidic device itis highly desirable to provide a control mechanism for the device whichis entirely free of mechanical moving parts. Also, it is still morepreferable if such control mechanism is to be inexpensively providedwithout causing substantial design change of the conventional fluidicdevice.

In operation of the fluidic device, switching control of the main flowof fluid is effected by causing a transverse pressure differentialacross the main flow of fluid sufficient to bias it to one or the otherof a pair of output or outlet ports. The desired transverse pressuredifferential is in turn created by applying control input in the form ofthe control flow of fluid through one or two control ports to the mainflow.

Incidentally, it is generally known to those well versed inhydrodynamics that the volumetric flow Qv and mass flow Qm of a viscousfluid flowing through a small and elongated passage such as a capillarytube or pipe could be expressed by the following formulas:

wherein A: Radius of the capillary tube 11.: Coefficient'of viscosity ofthe fluid through the tube v: Coefficient of kinetic viscosity of thefluid through the tube A P Pressure differential between the inlet andoutlet of the capillary tube L The length of the tube Considering now aready-to-vaporize liquid refrigerant such as one known under thetrademark of Freon R-l2, it has a coefficient of viscosity in gas formapproximately one twentieth of that in liquid form. While on the otherhand, it possesses a coefficient of knetic viscosity in gas formapproximately ten times as great as that in liquid state. Accordingly,as can be induced from the above mentioned formulas l and 2, the tubelength L and the pressure differential AP being the same the volumeticflow Qv of the refrigerant R-l2 as it passes the capillary tube in gasform increases greater than as it passes in liquid form, while its massflow as it passes the tube in gas form decreases substantially less thanas it passes in liquid form. The present invention is based on thisfluid phenomena and contemplates to use it in obtaining the desiredswitching control of the flow of fluid through fluidic devices.

It is, therefore, a primary object of this invention to provide a newand improved fluidic device for switching the flow of fluid with smallcontrol signals utilizing the above mentioned fluid phenomena.

It is another object of this invention to provide a new and improvedfluidic device for switching the flow of fluid which operates with highreliability for an extended period of time.

It is another object of this invention to provide a new and improvedfluidic device for switching the flow of fluid which has no mechanicalmoving parts.

It is another object of this invention to provide a new and improvedfluidic device for switching the flow of fluid having thermal meansoperative to produce necessary control signals.

It is still another object of this invention to provide a new andimproved refrigeration system having a plurality of evaporators and atleast one fluidic device of the nature described for controlling theflow of refrigerant to the evaporators in order to keep the temperaturesthereof within predetermined ranges.

It is still another object of this invention to provide a new andimproved refrigeration apparatus including a freezer compartment and afresh food compartment and having incorporated therein a fluidic deviceof the nature described for controlling the flow of refrigerant to oneor the other of the evaporators disposed within the freezer and freshfood compartments, respectively, thereby to maintain the freezer andfresh food compartments within their predetermined temperature range.

SUMMARY OF THE INVENTION In accordance with one aspect of thisinvention, there is provided a fluidic device comprising an inletpassage for receiving a heat vaporizable liquid and a main jet nozzlecommunicated with the inlet passage. The fluidic device also includes apair of outlet or output passages connected through an interactionregion to, the outlet of the jet nozzle. ready-to-vaproizable least one,preferably a pair of control passages are provided to connect the inletpassage with the interaction chamber by-passing the main jet nozzle.More specifically, a first control by-pass extends from one side wall ofthe inlet passage to a first control outlet formed in a one side wall ofthe interaction leading to the first outlet passage, while a secondcontrol by-pass extends from the other side wall of the inlet passage toa second control outlet made in the other side wall of the interactionchamber leading to the second outlet passage. A portion of theread-to-vaporizable liquid supplied to the inlet passage of the fluidicdevice is diverted into the control by-passes to be used as controlinput. Each of the control by-passes has heater means for vaporizingcontrol liquid through the by-passes. In order to direct the main streamof liquid to one or the other of the outlet passages, heater means ofthe control bypasses are selectively energized. If heating means of onecontrol by.-pass is energized and heating means of the other by-passcontrol is not energized the control liquid through the heated controlby-pass is vaporized into gas stream and the gaseous control fluid flowsthrough the control outlet into the interaction chamber. Due to asubstantially lower mass flow of a gas stream through a small passagesuch as a capillary tube with respect tothat of a liquid stream, the

vaporization of the control liquid through one control by-pass creates asufficient transverse pressure differential across the main stream ofliquid through the interaction chamber which tends to bias it to theside wall of the interaction chamber wherein the gaseous control fluidis flowing from the control outlet. The main stream of liquid then flowsout the outlet passage communicating with this this side wall. For thepurpose of causing a greater reduction in the mass flow of the vaporizedcontrol flow as it passes the control by-pass, the control by-passmaypreferably be so designed that the portion of the by-pass downstreamof the heater means has a greater flow resistance than the portionupstream of heater I means. In accordance with the present invention,this may be accomplished in varied ways. In one way, the control by-passmay be made to have a longer downstream portion than the upstreamportion. Or it may be formed to have a greater cross sectional flow areain the downstream section than in the upstream section. Alternatively,suitable flow restricting means in the form of a constriction or orificemay be provided in the control by-pass at a position downstream of theheater.

In accordance with the present invention, there is also provided arefrigeration system including a pair of evaporators and means forsupplying circulating a liquid refrigerant to both of the evaporatorsand a fluidic device of the nature described. The fluidic device isprovided between refrigerant supplying means and a pair of theevaporators with its inlet passage connected to refrigerant supplyingmeans for receiving the refrigerant and each of its two outlet passagesconnected to respective one of the evaporators. Heater means of thefirst control by-pass is so related to a first evaporator that theenergization of the heater may depend on the temperatures of the firstevaporator. Heater means of the second control by-pass is also relatedto the second evaporator in the same manner. When the temperature of thefirst evaporator rises to a predetermined value, heater means on thefirst control by-pass is automatically energized to bias the flow ofrefrigerant through the fluidic device toward the first outlet passagefor flow into the evaporator. The energization of the heater iscontinued until such time as the temperature of the first evaporatorreaches to a predetermined lower level. Similarly, when the temperatureof the second evaporator rises to a predetermined upper level, heatermeans on the second control by-pass is automatically turned on therebyto switch the flow of refrigerant through the fluidic device for flowthrough the second outlet passage and into the second evaporator. Theheater is kept in energized state until a desired minimum temperature ofthe second evaporator is attained. The temperatures of the twoevaporators are thus maintained within the desired ranges through theautomatic switching control over the flow of refrigerant by the fluidicdevice.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a plan view showing the basic profile of a fluidic elementembodying one form of this invention and having control by-pass with alonger flow path downstream of heating means;

FIG. 2 is a plan view showing the basic profile of a fluidic elementembodying another form of this invention and having control by-passeswith a flow path of reduced cross sectional area at the downstream ofheating means;

FIG. 3 is a plan view showing the basic profile of a fluidic elementembodying another form of this invention and having control by-passesformed with a constriction at a point downstream of heating means;

FIG. 4 is a plan view showing the basic profile of a fluidic deviceembodying still another form of this invention and having controlby-passes provided with a constriction at a point within heating means;

FIG. 5 is a graphic representationshowing the relation of the mass flowof gaseous control fluid through the control by-passes with respect tothe pressure differential between inlet and outlet end portions of thecontrol by-passes of a fluidic element which has no constriction in itscontrol by-passes;

FIG. 6 is a graphic representation showing the relation of the mass flowof gaseous control fluid through the, control by-passes with respect tothe pressure differential between inlet and outlet end portion of thecontrol by-passes of a fluidic element according to this invention andhaving a constriction in its control bypasses;

FIG. 7 is an exploded perspective view in enlarged scale of a fluidicdevice made in accordance with the present invention; and

FIG. 8 is a schematic diagram showing a multievaporator typerefrigeration system having a fluidic device of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawing and in particular to FIG. 1, there is schematically illustratedthe basic configuration or profile of a wall attachment type fluidicelement embodying one preferred form of this invention. As shown, thefluidic element includes an inlet passage 10, for receiving supply fluidthrough the element. The inlet passage 10 communicates through a reducedpower nozzle portion 12 with an enlarged interaction region or chamber14 which in turn is communicated with a pair of diverging outlet oroutput passages 16 and 18.

A pair of small elongated control passages 20 and 22 are symmetricallyprovided to connect the inlet passage to the interaction region 14by-passing the nozzle portion 12. More specifically, one control by-passhas an inlet port 21a provided in one side wall of the inlet passage andextends in general fonn of U to an control outlet 21b formed in thecorresponding side wall 24 of the interaction region at a point adjacentand just downstream of the nozzle section 12. Similarly, other controlby-pass 22 has an inlet opening or port 22a formed in the other sidewall of the inlet passage 10 at a location directly opposite the inletport 21a of the first control by-pass 20 and extends in general U formto a control outlet 22b made in the corresponding side wall 26 of theinteraction chamber at a point adjacent and downstream of the nozzlesection in direct opposite relation with respect to the outlet 21b ofthe first U- shaped control by-pass. For the purpose of hereinafterexplained, electric heater means 28 and are provided around the by-passcontrol passages 20 and 22, respectively, at a suitable location thereofto partially cover the passages. vl

With this construction of the fluid element, a suitable heat vaporizableliquid such as the liquid refrigerant known under the trademark of FreonR-l2 is supplied to the inlet passage 10 and it flows through the mainnozzle 12 in power jet into the interaction chamber 14. Meanwhile,-aportion of supply liquid provided to the inlet passage is diverted tothe control by-passes 20 and 22 and flows through their respectivecontrol outlet into the interaction chamber 14 of the fluid device asindicated by the arrows.

In order to direct the main stream of liquid through the fluidic deviceto one or the other of the outlet passages 16 and 18, in accordance withthe usual fluid amplifier practice, a sufficient transverse pressuredifferential must be created across the main stream of liquid as itemerges in power jet from the nozzle which tends to bias it toward oneof side walls 24 and 26 of the interaction chamber for flow therealong.For this purpose in accordance with the present invention the heaters 28and 30 may be selectively energized. More specifically, if the firstheater element 28 placed to partially surround the first control by-pass20 is energized, the control flow of liquid through the first controlbypass is heated up to substantially vaporize into gas phase by theheater and the vaporized gas stream flows out the control outlet 21b ofthe first control by-pass. As explained hereinabove, when the control loliquid flow is turned into a gas stream in the small elongated by-passcontrol passage 20 its mass flow is substantially decreased. While onthe other hand, since the second heater element 30 disposed to partiallysurround the second control by-pass 22 is not yet energized the con trolflow passes the by-pass in normal liquid form with relatively highermass flow rate as compared with the gaseous control flow through thefirst control by-pass.

An incessant flow of the power jet emerging from the nozzle through theinteraction chamber tends to draw or entrain the control flows out ofthe both control bypasses 20 and 22. Under the above mentioned conditiona relatively large amount of control fluid is drawn from the non-heatedsecond control by-pass than from the heated first control by-pass asviewed in terms of the mass flow. The fact is due to the describeddifference of the mass flow of fluid in its liquid state and gas state.As the result, the pressure in the area of the first control outlet 21bof the heated first control bypass decreases with respect to the secondcontrol outlet 22b of the non-heated second control by-pass which willcause a transverse pressure differential across the main jet stream ofliquid through the interaction chamber 14. This transverse pressuredifferential tends to cause the stream of liquid to attach itself to theside wall 24 of the interaction chamber where the control outlet 21b ofthe first control-by-pass is made so that it will flow out through thefirst outlet passage 16.

On the other hand, if the first heater 28 is deenergizecl and the secondheater 30 of the second control by-pass 22 is then energized, thecontrol liquid into the second control by-pass is substantiallyvaporized by the heater and flows through the control by-pass in gasstream. The portion of the control liquid diverted into the non-heatedfirst control by-pass 28 flows therethrough in liquid form. Due to arelatively small mass flow of the gaseous control fluid through theheated second control bypass 22 with respect to that of the controlliquid through the first control by-pass 20, a transverse pressuredifferential is created in substantially the same manner as discussedabove across the main jet stream of liquid through the interactionchamber which tends to cause the main liquid stream to detach itselffrom side wall 24 and switch over into attachment to side wall 26 sothat it will flow out through the second outlet passage 18.

When it is desired to switch the main stream of liquid back to the firstoutlet passage 16, the second heater 30 is turned off and the firstheater element 28 of the first control by-pass is again turned on tovaporize the control liquid through the first by-pass. The fluidicelement of the present invention may be sodesigned that the main liquidstream through the element may flow out the both outlet passages atsubstantially the same rate under such condition where no control signalare applied i.e. neither of the two control heaters 28 and 30 isenergized. It may also be designed such that both of the heaters arenormally energized providing a no signal or control state and they areadapted to be selectively deenergized to switch the main liquid flow toeither the first or second outlet passage.

As can be easily understood by those skilled in the art, when avaporizable fluid is to be heat vaporized in a small passage such as acapillary tube or the like it causes an instantaneous pressure rise andthe generated high pressure proceeds through the passage. If such highpressure occurring in the control by-pass during heat vaporization ofthe control liquid by the heater, it proceeds downstream through thecontrol by-pass and tends to disturb the desired low pressure conditionwhich is produced in the area of the control outlet as the result of adecrease in the mass flow of the control fluid caused by the heatevaporation. This in turn may disturb the desired transverse pressuredifferential across the main liquid stream and result in erraticoperation of the fluidic element during which the stream of liquidcannot be switched over to the desired direction. Accordingly, it isessential to provide means for preventing the instantaneous highpressures from proceeding downstream through the control by-passes.

Moreover, in order to provide a quick and assured switching of the mainstream of liquid through the area of the other of the control outlets.As is apparent ,from the foregoing description, a greater pressurereduction at a control outlet may be attained through reducing the massflow of the control fluid through the corresponding control by-pass to agreater extend. One way to achieve this is to have a greater resistanceagainst the mass flow of the control fluid.

According to this invention, in order to attain the above describedpurposes, the control by-passes are so designed to have a greater flowresistance in the portion downstream of the heating elements than in theportion upstream of the heating elements. In the fluid deviceillustrated in FIG. 1, this has been accomplished by making thedownstream flow sections 32 and 34 of the control by-passes and 22between the respective heater elements 28 and 30 and control outputs 21band 22b much longer than the upstream flow sections 36 and 38 betweenthe respective heater elements and inlet openings 21a and 22a. With thisarrangement of the control by-passes 20 and 22, the instantaneous highpressures occurring at the heating sections during heat vaporization ofthe control flows of liquid by the heaters 28 and 30 are not allowed toproceed downstream through the by-passes to interaction chamber due to agreater flow resistance of the downstream flow sections 32 and 34.Instead, the high pressures move upstream from the heating sectionsthrough the upstream flow sections 36 and 38 of a lower flow resistanceinto the inlet passage 10. Accordingly, any possibility of the highpressures caused at the heating sections of the control by-passesadversely affecting the desired low pressure conditions at the controloutlets, thus the desired transverse pressure differential across themain flow of liquid through the interaction chamber is effectivelyeliminated assuring normal expected control operation of the fluidicdevice. Moreover, the longer flow passage of the control by-passesdownstream of the heating elements presents a larger flow resistanceagainst the gaseous control stream produced at the heating sections andmoving downstream through the control by-passes. This is effective inadditionally reducing the mass flow of the gaseous control fluid, whichin turn assists in creating a greater transverse pressure differentialacross the main stream of liquid through the fluidic device.

In the embodiment illustrated in FIG. 2, the desired greater flowresistance in the portion of thecontrol bypasses downstream of theheater elements is provided by making downstream flow sections 32 and 34to have a smaller diameter than the upstream flow sections 36 and 38.The construction is also effective in preventing the high pressurecaused at the heating sections of the control by-passes from proceedingdownstream therethrough and in crating a greater transverse pressuredifferential across the main liquid stream through a reduction in themass flow of one control fluid.

In another embodiment illustrated in FIG. 3, the control by-passes 20and 22 are respectively formed with constrictions 40 and 42 in the formof an orifice at a location. adjacent and downstream of the heatingelements 28 and 30. The constriction orifices 40 and 42 adds asufficient flow resistance to the downstream sections 32 and 34 of thecontrol by-passes which performs a dual function of preventing theinstantaneous high pressures caused at the heating section during theheat vaporization of the control liquid from proceeding downstreamthrough the control by-pass as well as reducing substantially the massflow of vaporized control fluid as it passes the downstream section inthe I manner essentially similar manner as explained above. These flowrestricting constrictions are advantageous in that they eliminate theneed of a longer downstream flow path as is the case with the fluidelement of FIG. I. The fact enables a small and compact construction ofa fluidic element.

An additional feature of accomplishing a higher heat vaporizationefficiency may be obtained by making the constricted parts 40 and 42within the heating sections of the control by-passes 20 and 22 i.e.within the portions of the control by-passes surrounded by the heaterelements 28 and 30 as shown in FIG. 4. This is attributed to the factthat it is easy to heat the stream of liquid flowing through a narrowerspace. The constrictions or orifices 40 and 42 provide narrower spacesthrough which the control liquid to be heat vaporized flows.

The benefit of forming constricted orifices in the control by-passes canalso be clearly understood with reference to FIGS. 5 and 6 which show ingraphic representation the relation of the mass flow of the controlfluid through the downstream section of the control by-pass with respectto the pressure differential between the opposite ends of the downstreamsection.

If the fluidic element of this invention has no constric- 1 tions in itscontrol by-passes, the relationship between the control fluid flowthrough the downstream section and the pressure differential generallypresents itself as shown by the straight line in FIG. 5. Thus, as thepressure differential between the opposite ends become greater due tohigher pressure occuring upstream of the orifice the mass flow of thecontrol fluid through the downstream section of the control by-passincreases accordingly. In other words, if the control by-pass has noconstriction orifice any pressure rise caused in the portion of thecontrol by-pass upstream of the orifice-may give direct and undesirableeffect upon the mass flow of gaseous control fluid through thedownstream section of the control by-pass in that an increase in themass flow of the gaseous control fluid brings about a correspondingpressure rise in the area of the control outlet resulting in a failureof creating a sufficienttransverse pressure differential across the mainstream of in the mass flow reduces to such small degree as to beconsidered substantially zero phrased differently, unusual higherpressure condition occuring in the portion of the control by-passupstream of the constriction gives no substantial increase in the massflow of the gaseous control fluid through the downstream section of thecontrol by-pass and, accordingly, the gaseous control fluid flows atessentially the same predetermined rate independent of the upstreamhigher pressure thereby to create the desired transverse pressuredifferential across the main stream of liquid through the fluidicelement. This is entirely due to the fact that the presence of theconstrictions in the control bypasses is effective to preventundesirable upstream higher pressure from proceeding downstream throughthe control by-passes. Thus, the simple constrictions provides effectiveand inexpensive means for assuring the proper, expected operation of thefluidic element.

FIG. 6 illustrates in exploded perspective view a typical fluid deviceconstructed in actual practice according to teaching of this invention.The fluid device includes a top cover member 55 and a bottom base member52 made preferably of a suitable synthetic resin material. The uppersurface of the base member 52 is recessed downwardly in generalaccordance with the basic profile disclosed in FIGS. 1 to 4, thereby toform essential fluid flow paths. The recessed portion .comprises aninlet passage 54 for receiving source fluid. The inlet passagecommunicates through a power jet nozzle 56 of reduced width with arelatively enlarged interaction region 58 defined by spaced, elongatedside walls 60 and 62. These side walls extend in diverging mannertowards the lower end of the bottom base member 52 and terminate at thesemicircular end wall 64 and 66. A V-shaped intermediate splittersection 68 is formed between the diverging side walls 60 and 62 at theend opposite the inlet end. The side wall 60 and the intermediatesection 68 define a first outlet or output passage 70, while side wall62 and the intermediate section 68 define second outlet or outputpassage 72, with both of the outlet passages communicating with theinlet passage 54 through the interaction chamber 58 and the restrictedpower jet nozzle 56.

The recessed profile further includes a pair of upper control inlets 74and 76 which are generally perpendicularly connected to the oppositeside walls of the inlet passage 54 at their one end and terminate attheir other end in circular holes 74a and 76a, respectively. Thecontrolinlets 74 and 76 are substantially identical in configuration andare disposed in mutual alignment. A pair of control outlets similar tothe control inlets are formed to extend generally perpendicularly to thedirection of the main stream of liquid through the device. As shown, thecontrol outlets 78 and 80 communicate at their one end with theinteraction chamber 58 through outlet ports 78b and 80b formed in directopposite alignment in side walls 60 and 62 at positions adjacent andjust downstream of the power nozzle 56. The other ends of the controloutlet 78 and 80 terminate in circular holes or cavities 78a and 80a,respectively.

The top cover member 50 is adapted to be superimposed on the bottom basemember 52 and includes a relatively large inlet opening 82 made inalignment with the upper or upstream end portion of the inlet passage54. it also has a pair of relatively large outlet or output openings 84and 86 formed in positions corresponding planted in the outlet openings84 and 86, respectively.

A U-shaped tube 94 of relatively small diameter is vertically set up inthe upper member 94 such that one open end of the tube may come intoregistry and communication with the recessed circular cavity 74a of theone control inlet 74, while the other open end with the recessedcircular cavity 780 of the one control outlet 78 on the same side as thecontrol inlet 74 when the top cover member 50 is placed in position onthe bottom base member 52. A second generally U-shaped control tube 96substantially similar to the first mentioned control tube 94 is also setvertically on the top cover member 50 such that one open end of the tubemay be brought in registry and communication with the recessed circularcavity 76a at the end of the right control inlet 76 while the other openend with the recessed circular cavity a at the end of the right controloutlet 80.

As shown in the drawing, the first and second control tubes 94 and 96are equipped with electric heater 98 and 100. Heaters 98 and 100 areplaced in heat transfer relationship to partially surround the tubes 94and 96, respectively, at a position adjacent their upper ends. Theseheaters may suitably be connected to electric power supply throughcontrol means. The control tubes have also formed therein constrictions102 and 104 at a location closest to the electric heaters 98 and 100.

With the above arrangement, when the top cover member 50 is assembled inplace on the bottom base member 52 to complete a fluid device, the firstU- shaped control tube 94, left control inlet 74 and left control outlet78 together form a first control by-pass of the fluid device togetherform a first control by-pass which corresponds to the first controlby-pass 20 shown in the basic profiles of FIGS. 1 to 4. The second U-shaped control tube 96, right control inlet 76 and right control outlet80 form a second control by-pass corresponding to the second controlby-pass 22 of the basic profiles. It should be appreciated that in orderto obtain better control results the first and second control by-passmeans should preferably made such that they are precisely identical inconstruction and size. The top cover member 50 and bottom base member 52are assembled together in tight sealing engagement to complete a fluiddevice.

In operation of the fluid device, a suitable vaporizable operationliquid supplied through the inlet conduit 88 to the inlet passage 54.Substantial portion of the source liquid provided to the inlet flowsthrough the main jet nozzle 58 into the interaction chamber 58 while arelatively small amount of the liquid is diverted into the pair of thecontrol tubes 94 and 96 through the control inlets 74 and 76. Thediverted control liquid flows through the control tubes the controloutlets 78 and 80 and into the interaction chamber 58 when the electricheater 98 on the first control tube 98 is energized to heat vaporizethe'control liquid through the tube, the transverse pressuredifferential across the main liquid stream through the interactionchamber is such that the main stream is caused to attach itself to theside wall 60 and it will flow out through the first outlet passage 70.While on the other hand, when the first. heater is deenergized and theelectric heater 100 of the second control tube 96 is energized thecontrol liquid through the tube is vaporized to create a sufficienttransverse pressure differential across the main stream of liquid whichtends to cause it to detach from the side wall 60 into attachment to theside wall 62. The main stream of liquid is thus switched from the sidewall 60 to side wall 62 so that it will flow out the second outletpassage 72. When it is desired to switch the main stream of liquid backto the first outlet passage, the second heater 100 may be deenergizedand the first heater 98 is again energized. Under no control signalcondition i.e. under such condition where both of the heaters 98 and 100are deenergized, the main stream of liquid through the fluidic devicemay flow out through both of the outlet passages 70 and 72 atsubstantially the same rate. Of course, it is also possible to operatethe fluidic device in such manner as to permit the main liquid stream toflow out through both of the outlet passages only when two heaters aresimultaneously energized.

The control tubes may preferably be formed to receive control liquid inan amount less than 2 percent of the source liquid provided to the inletpassage. A smaller amount of the control liquid makes it easier tovaporize by a heater of smaller heating capacity. As an example, theby-pass control tube may be 0.2 mm in diameter and 150 mm in length ifit has no contriction orifice-The power jet nozzle may be formed to havea diameterand length of 0.5mm and 1.0mm, respective- In FIG. 8, there isschematically illustrated a multievaporator type refrigerant, circuitfor a combination refrigerator having the fluidic device of the presentinvention incorporated therein. The refrigerant circuit comprises amotor compressor 120, a condenser 122, flow restricting means in theform .of a capillary tube 124 and a pair of evaporators 126 and 128. Oneevaporator 126 is provided for cooling a freezer compartment 126a of acombination refrigerator adapted to operate at a temperature belowfreezing and the other evaporator 128 is provided for cooling a freshfood compartment 128a intended to operate at an above freezingtemperature. In accordance with the usual refrigerator practice, thecomponent parts are to be connected in closed series flow relationshipin order to form a closed refrigerant circuit. As shown in FIG. 8, themotor compressor 120, the condenser 122 and the flow restrictingcapillary tube 124 are series connected. For controlling the supply ofthe refrigerant to the two evaporators 126 and 128, thus thetemperatures within the compartments 126a and 128a, fluid device 130 ofthe present invention is provided in the refrigerant circuit between thecapillary tube 124 and the two evaporators. More specifically, inletpassage 131 of the device is connected to the outlet of the capillarytube 124 for receiving the flow of refrigerant from the capillary tube,while a first and second outlet passages 132 and 133 are communicatedrespectively with the inlets of the evaporators 126 and 128 fordirecting the flow of refrigerant thereinto. Outlets of the evaporatorsare jointly connected to the compressor 120. The

refrigerant circuit is further associated with a suitable operationalcircuit means indicated by the reference numeral 140. The operationalcircuit 140 is operatively connected to motor compressor 120, firstand'second heating elements 134 and 135 provided on first and secondcontrol by-passes 136 and 137, and also with temperature sensing meansl26b and 128b disposed within freezer and fresh food compartments 126and 128. As hereinafter explained in more detail, the opera tionalcircuit 14 functions to control the energization of the heaters and themotor compressor in response to the temperatures within the freezer andfresh food compartments detected by temperature sensing means 126b and128b.

With the above mentioned arrangement of the refrigerant, duringoperation the liquid refrigerant is circulated by the compressor throughthe con-v denser 122, flow restricting capillary tube 124 to the fluidicdevice 130. Now, if a predetermined lower temperature is not yetattained in the freezer compartment 126a, the operational circuit 140maintains the heater element 134 on the first control by-pass 136 inenergized state to heat up the control liquid flow through the by-passinto gas. As described hereinabove, this results in a transversepressure differential across the main stream of refrigerant as itemerges from power jet nozzle 138 into interaction chamber which tendsto bias it toward the first outlet passage 132 for flow therethrough andinto the first evaporator 126. A continued flow of refrigerant throughthe evaporator 126 cools down the freezer compartment 12611. When thetemperature within the freezercompartment 126a reaches a predeterminedlower level, temperature sensing means 126b gives a suitable signal tothe operational circuit 140. The operational circuit in turn operates toturn off the heater element 134. The motor compressor 120 issimultaneously turned off excepting when a refrigeration is called forin the fresh food compartment. Circulation of the refrigerant to thefirst evaporator is then stopped until the temperature within thefreezer compartment rises to a predetermined upper level, when theoperational circuit 140 is caused to energize the heater 134 and thecompressor 120 by a signal produced and supplied by temperature sensingmeans 126a. If a refrigerating operation is required for the fresh foodcompartment since a present lower temperature is not yet attained, theoperational circuit 140 functions to keep the compressor energized andactuates the heater element of the second control bypass 137. The mainstream of refrigerant is then switched back from the first outletpassage 132 to the second outlet passage 133 so that it will flow intothe second evaporator 128 thereby to cool down the fresh foodcompartment 128. When the temperature within the fresh food compartmentreaches a predetermined lower value, temperature sensing means 128aprovide a requisite signal to the operational circuit 140. Upon receiptof which the circuit deenergizes the second heater 135. The compressor120 is also simultaneously turned off excepting when a refrigeration iscalled for in the freezer compartment. The heater 135 is kept turned offuntil such time as the temperature within the fresh food compartmentrises to a predetermined upper value, when the heater 135 and thecompressor 120 are again energized by the circuit 140.

Under such unusual condition where refrigerating operation is called forin both of the compartments, the operational circuit is so designed thatit functions to give a priority supply of refrigerant to one or theother of the two evaporators upon considering all informations providedto the circuit. If, on the other hand, neither of the two compartmentscalls for refrigerating operation, the operational circuit 140 keeps thecompressor 120 turned off resulting in a complete stoppage of thesystem.

In alternative way, it is also possible to design the system such thatthe main stream of refrigerant may be normally biased for flow throughthe first outlet passage into the first evaporator and it may beswitched over for flow through the second outlet passage to the secondevaporator whenever the refrigeration of the fresh food compartment isrequired.

Freon is used as a liquid refrigerant in the refrigerant circuit of FIG.8, a one wattage heater is sufficient to vaporize the control liquidinto gas although it depends on the flow rate of the liquid through thecontrol bypass.

Whilev there has been illustrated and explained hereinabove fluidicdevices including a pair of control by-passes each having its ownheating element, it should be noted that a fluidic device having onlyone control by-pass with an associated heater element may be made andfunction to brings about the desired flow control results.

From the foregoing description, it is appreciated that v in the fluidicdevice of the present invention the transverse pressure differentialacross the main stream of liquid necessary for the switching control iscreated through the thermal vaporization of the control liquid. The facteliminates the need of mechanical valve means which was an essentialpart of the conventional fluidic devices. A complete elimination ofmechanical moving part from a fluidic device assures a long, reliableand trouble free control operation and also extends an effectiveoperational life of the device. Further, the control liquid for theswitching operation of the main stream of liquid through the presentfluidic device is directly diverted from the main stream itself by meansof the control by-pass and, therefore, no separate source of controlliquid and its associated mechanism are required resulting in a simpleas well as inexpensive construction of the entire device. The fact thatthe control liquid is obtained from the main liquid stream enables acomplete closed flow construction of the fluidic device and this in turnrenders the fluidic device of the present invention suitable for use invarious closed flow circuit applications such as refrigeration circuitswhere inflow of external and foreign fluid must be excluded. The amountof the required control liquid is so small in comparison with the mainstream of liquid that the diversion of the control liquid from themainstream inno way adversely affects the main flow. In this connec- 1.A fluidic device comprising an inlet passage for supplying heatvaporizable liquid; a main nozzle connected to said inlet passage; apair of outlet passages connecting through an interaction chamber to theoutlet of said main nozzle; means for biasing the flow of liquid fromsaid main nozzle toward a first of said outlet passages; at least oneby-pass control passage extending from said inlet passage to a controlport which is located near the outlet of said main nozzle and open inthe wall of the interaction chamber; said by-pass control passageincluding a heater therein to vaporize the liquid flowing through theby-pass control passage and being so constructed that the flowresistance in said bypass control passage is larger at the downstreamportion than at the upper stream portion with respect to the location ofsaid heater whereby vaporization of the liquid flowing through saidby-pass control passage causes a decrease in the mass flow in saidby-pass control passage which is inturn effective to divert the flow ofliquid from said main nozzle to the first outlet passage.

2. A fluidic device as defined in claim 1, in which said downstreamportion of said by-pass control passage comprises an elongated tube.

3. A fluidic device as defined in claim 1, in which the length of saiddownstream portion of said by-pass control passage is larger than thatof said upperstream portion.

4. A fluidic device as defined in claim 1, in which the flow sectionalarea of said downstream portion of said by-pass control passage issmaller than that of said upperstream portion.

5. A fluid device as defined in claim 1 inwhich a source of heatvaporizable liquid is provided in fluid communication with said mainnozzle.

6. A fluidic device as defined in claim 1 in which said downstreamportion of said by-pass control passage has a constriction.

7. A fluidic device as defined in claim 6, in which said constriction isprovided in the form of an orifice having a narrower diameter than theother portion.

8. A fluidic device as defined in claim 6, in which said constriction islocated close to the said heater.

9. A fluidic device comprising an inlet passage for supplying heatvaporizable liquid; a main nozzle connected to said inlet passage; apair of outlet passages connecting through an interaction chamber to theoutlet of said main nozzle; means for biasing the flow of liquid fromsaid main nozzle toward a first of said outlet passages; a pair ofby-pass control passages extending from said inlet passage to therespective control ports which are located near the outlet of said mainnozzle and opposedly open in the walls of the interaction chamber; atleast one of said by-pass control passages including a heater therein tovaporize the liquid flowing through the by-pass control passage andbeing so constructed that the flow resistance in said by-pass controlpassage is larger at the downstream portion than at the upperstreamportion with respect to the location of said heater whereby vaporizationof the liquid flowing said by-pass control passage causes a decrease inthe mass flow in said by-pass control passage which is in turn effectiveto divert the flow of liquid from said main nozzle to the second outletpassage.

10. A fluid device as defined in claim 9 including a source of heatvaporizable liquid in fluid communication with said main nozzle.

11. A fluidic device comprising an inlet passage for supplying heatvaporizable liquid; a main nozzle connected to said inlet passage; firstand second outlet passages connecting through an interaction chamber tothe outlet of said main nozzle; a pair of by-pass control passagesextending from said inlet passage to the respective control ports whichare'located near the outlet of said main nozzle and opposedly open atthe walls of said first and second outlet passages, respectively, eachof said by-pass control passages including a heater therein to vaporizethe liquid flowing through the bypass control passage and being soconstructed that the flow resistance in said by-pass control passage islarger at the downstream portion than at the upper stream portion withrespect to the location of said heater; and means for alternativelyoperating said heaters in said by-pass control passages wherebyvaporization of the liquid flowing through said by-pass control passagecauses a decrease in the mass flow in said by-pass control passage whichis in turn effective to divert the flow of liquid to the selected outletpassage connected to the by-pass control passage in which said heater isoperating.

12. A fluid device as defined in claim 11 including a source of heatvaporizable liquid in fluid communication with said main nozzle.

1. A fluidic device comprising an inlet passage for supplying heat vaporizable liquid; a main nozzle connected to said inlet passage; a pair of outlet passages connecting through an interaction chamber to the outlet of said main nozzle; means for biasing the flow of liquid from said main nozzle toward a first of said outlet passages; at least one by-pass control passage extending from said inlet passage to a control port which is located near the outlet of said main nozzle and open in the wall of the interaction chamber; said by-pass control passage including a heater therein to vaporize the liquid flowing through the by-pass control passage and being so constructed that the flow resistance in said by-pass control passage is larger at the downstream portion than at the upper stream portion with respect to the lOcation of said heater whereby vaporization of the liquid flowing through said by-pass control passage causes a decrease in the mass flow in said by-pass control passage which is inturn effective to divert the flow of liquid from said main nozzle to the first outlet passage.
 2. A fluidic device as defined in claim 1, in which said downstream portion of said by-pass control passage comprises an elongated tube.
 3. A fluidic device as defined in claim 1, in which the length of said downstream portion of said by-pass control passage is larger than that of said upperstream portion.
 4. A fluidic device as defined in claim 1, in which the flow sectional area of said downstream portion of said by-pass control passage is smaller than that of said upperstream portion.
 5. A fluid device as defined in claim 1 in which a source of heat vaporizable liquid is provided in fluid communication with said main nozzle.
 6. A fluidic device as defined in claim 1 in which said downstream portion of said by-pass control passage has a constriction.
 7. A fluidic device as defined in claim 6, in which said constriction is provided in the form of an orifice having a narrower diameter than the other portion.
 8. A fluidic device as defined in claim 6, in which said constriction is located close to the said heater.
 9. A fluidic device comprising an inlet passage for supplying heat vaporizable liquid; a main nozzle connected to said inlet passage; a pair of outlet passages connecting through an interaction chamber to the outlet of said main nozzle; means for biasing the flow of liquid from said main nozzle toward a first of said outlet passages; a pair of by-pass control passages extending from said inlet passage to the respective control ports which are located near the outlet of said main nozzle and opposedly open in the walls of the interaction chamber; at least one of said by-pass control passages including a heater therein to vaporize the liquid flowing through the by-pass control passage and being so constructed that the flow resistance in said by-pass control passage is larger at the downstream portion than at the upperstream portion with respect to the location of said heater whereby vaporization of the liquid flowing said by-pass control passage causes a decrease in the mass flow in said by-pass control passage which is in turn effective to divert the flow of liquid from said main nozzle to the second outlet passage.
 10. A fluid device as defined in claim 9 including a source of heat vaporizable liquid in fluid communication with said main nozzle.
 11. A fluidic device comprising an inlet passage for supplying heat vaporizable liquid; a main nozzle connected to said inlet passage; first and second outlet passages connecting through an interaction chamber to the outlet of said main nozzle; a pair of by-pass control passages extending from said inlet passage to the respective control ports which are located near the outlet of said main nozzle and opposedly open at the walls of said first and second outlet passages, respectively, each of said by-pass control passages including a heater therein to vaporize the liquid flowing through the by-pass control passage and being so constructed that the flow resistance in said by-pass control passage is larger at the downstream portion than at the upper stream portion with respect to the location of said heater; and means for alternatively operating said heaters in said by-pass control passages whereby vaporization of the liquid flowing through said by-pass control passage causes a decrease in the mass flow in said by-pass control passage which is in turn effective to divert the flow of liquid to the selected outlet passage connected to the by-pass control passage in which said heater is operating.
 12. A fluid device as defined in claim 11 including a source of heat vaporizable liquid in fluid communication with said main nozzle. 